Roundtower NHL 3.5 Light Grey is a versatile, moderate-strength Natural Hydraulic Lime binder, ideal for masonry, pointing, rendering, and external plasterwork. Its light grey tone offers a more natural appearance when matching stone or traditional mortars, particularly in new build applications or sympathetic restoration work.
Manufactured from high-purity limestone and conforming to EN 459-1 standards, Roundtower NHL 3.5 Light Grey provides a durable, breathable, and environmentally responsible alternative to cement-based binders, ensuring long-term compatibility with traditional masonry and modern breathable wall systems.
Key Benefits
✅ Moderate Strength – Perfect for general-purpose masonry and render applications.
✅ Natural Light Grey Colour – Ideal for projects requiring a softer, stone-compatible mortar tone.
✅ Breathable & Vapour Open – Allows moisture to escape, reducing the risk of damp and condensation.
✅ Self-Healing Properties – Free lime content promotes autogenous crack repair over time.
✅ Eco-Friendly Choice – Lime production uses less energy and reabsorbs CO₂ during curing.
✅ Recyclable Masonry – Stone or brick set in lime mortar is easier to dismantle and reuse.
Applications
🔹 External Rendering & Lime Harling – Breathable finish for stone, brick, or solid wall backgrounds.
🔹 Bedding & Pointing Mortars – Suitable for both modern and historic masonry.
🔹 Scratch & Float Coats – Use in multi-layer lime plaster systems, especially where a subtle grey tone is preferred.
🔹 New Build Construction – Widely used in ecological builds and traditional-style developments.
🔹 General Masonry Work – Ideal for breathable construction and conservation-compatible mortars.
Technical Specifications
| Property | Value |
|---|---|
| Compressive Strength (28 days) | 5.6 MPa |
| Setting Time | 337 minutes |
| Free Lime Content | 25.4% |
| Whiteness (Visual) | Light grey |
| Fineness (90 µm) | 5.6% retained |
| Fineness (200 µm) | 1% retained |
| Expansion | 0.2 mm |
| Bulk Density | 0.779 g/cm³ |
| Real Density | 2.77 g/cm³ |
| Blaine Surface Area | 8,872 cm²/g |
| SO₃ Content | 1.7% |
| Standard Compliance | EN 459-1 (NHL 3.5) |
| Packaging | 25 kg paper bags (56 per pallet) |
Usage & Storage Advice
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Use the minimum water required for a workable mix to avoid cracking. Dampen substrates the day before and prior to application, allowing the surface water to be reabsorbed. Avoid rapid drying due to high temperatures, direct sunlight or strong winds by covering and curing with a light water mist as necessary.
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Work between 5°C and 30°C, and protect from frost, rain, or excessive heat during setting. We always advise following best practices for curing and protecting fresh lime mortars and renders from direct sunlight and wind using hessian sheeting, which acts as a barrier between the freshly applied lime and the environment.
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Store dry, off the ground, and use within 12 months of production date.
Why Choose Roundtower NHL 3.5 Light Grey?
Roundtower NHL 3.5 Light Grey is a durable, breathable, and visually sympathetic lime binder for modern lime mortars and renders. Its reliable strength and gentle tone make it especially useful for new builds, masonry restoration, and breathable wall systems where a natural look and conservation values are important.
